A study published in the Journal of Managed Care & Specialty Pharmacy found that filgrastim and filgrastim-sndz were noninferior for the prevention of febrile neutropenia events that would require hospitalization. However, inferiority could not be established for serious adverse events.

There are no significant differences between filgrastim and its biosimilar filgrastim-sndz in the prevention of febrile neutropenia events that require hospitalization, according to a study published in the Journal of Managed Care & Specialty Pharmacy.

In March 2015, filgrastim-sndz, a granulocyte-colony stimulating factor (G-CSF), was introduced as a biosimilar to filgrastim. The biosimilar shares 5 FDA-approved indications with filgrastim.

“While filgrastim-sndz and filgrastim have been shown to be highly similar with no clinically meaningful differences in reducing the incidence of febrile neutropenia in a randomized controlled trial setting where patient selection, conditions, and observations may be more ideal, comparative effectiveness for filgrastim versus filgrastim-sndz has not been studied to date using observations from real-world practice,” wrote the authors of the study.

The retrospective cohort study used administrative claims from the Humana Research Database to target patients receiving G-CSF post-chemotherapy. Patients enrolled in a Medicare Advantage Prescription Drug Plan with a claim for a G-CSF from October 1, 2015, to September 30, 2016, were included in the study. The G-CSF claims had to occur within 6 days of exposure to chemotherapy and without any subsequent chemotherapy within 14 days of G-CSF use.

The amount of patients with a febrile neutropenia outcome that required hospitalization and the amount of patients that experienced a potential serious adverse event after G-CSF use were observed in the 14 days following the index date. Febrile neutropenia requiring hospitalization was measured in 2 ways:

A broad definition: hospitalization with a diagnosis of neutropenia

A narrow definition: required hospitalization with both neutropenia and infection diagnoses

Of the 189 participants, 88 had a medical or pharmacy claim for filgrastim, and 101 had a claim for filgrastim-sndz. When comparing filgrastim and filgrastim-sndz, noninferiority was determined based on both the broad and narrow definitions for febrile neutropenia requiring hospitalization, with –0.6% (90% CI, –5.1%-4.0%, P = .84) and –0.8% (90% CI, –3.8%-2.1%, P = .64) incidence differences, respectively.

Filgrastim had only a slightly higher incidence rate of serious adverse events, but the difference was too large to determine noninferiority (2.5%, 90% CI, –7.5%-2.5%, P = .42).

“An incidence difference of less than 1% was selected as the margin of noninferiority for this study, but determining the boundaries for noninferiority analysis is not well defined and is especially nebulous when conducting real-world and observational studies,” wrote the authors.

Overall, results showed that while filgrastim and filgrastim-sndz were noninferior for the prevention of febrile neutropenia events that would require hospitalization, inferiority could not be established for serious adverse events.